AirHint found the following cheapest return flights from Seattle (SEA) to Sydney (SYD) in August 2025 (see full year).

Return flights

13 Aug - 16 Sep	Air Canada
07 Aug - 10 Aug	Air Canada
01 Aug - 05 Aug	Air Canada
01 Aug - 14 Aug	Air Canada
17 Aug - 20 Aug	Air Canada
21 Aug - 29 Aug	Air Canada
20 Aug - 29 Aug	Air Canada
20 Aug - 28 Aug	Air Canada
29 Aug - 02 Sep	Air Canada
27 Aug - 03 Sep	Air Canada
22 Aug - 04 Sep	Delta
08 Aug - 10 Aug	United
24 Aug - 04 Sep	ANA
27 Aug - 02 Sep	ANA

Also check the deals for one-way flights from Seattle to Sydney in August.

The deals are updated regularly. The prices may go up as tickets are purchased by other travellers. Only the cheapest flights are offered. Select a price to book and secure these cheap prices.

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Cheapest return flights from Seattle to Sydney in August from 648€

Return flights